This invention relates generally to a system for converting solar energy into electrical energy and more specifically, to a system that will utilize solar energy for multiple purposes including electrical energy and for the production of potable water for drinking and irrigation purposes.
Solar radiation comes to the earth at an average rate of approximately 1.35 kilowatts per square meter. This is the so called solar constant, (frequently given as 1.94 cal/cm.sup.2 min).
The total solar radiation intercepted by the earth is 1.73.times.10.sup.17 watts which is equivalent to about 75,000 times the total power used in the United States during 1970. Stated in a different way, in 1970, the land area of the United States received from the sun about 1000 times as much energy as it consumed. In passing through the atmosphere a fraction of this radiation is scattered away from the earth. The fraction reaching the surface of the earth, however, is quite substantial. Since the potential benefits from extensive use of solar energy are so great it is imperative to explore the possibilities of using it on a large scale to meet the long range energy needs of the human race.
Various large scale schemes have been proposed for tapping this source of power which is practically of infinite duration (about 200 million human generations). By comparison the expected durations of some other sources of energy are
petroleum: 1-2 human generations PA1 coal: 15-20 human generations PA1 "atomoic fuel": 50-100 human generations
(1 human generation is considered to be about 30 years.)
A solar sea power scheme proposes to use the temperature difference between the ocean surface water and the bottom to run a thermal engine. Such installations would be located preferentially in deep tropical waters where the temperature differences are higher and less variable than elsewhere. The central tower solar farm concept proposes to use a large field of sun tracking mirrors which reflect the solar radiation to a boiler on top of a central tower. The concentrated solar power is used then to drive a thermal engine at relatively high temperatures. Although not stated by the proposers of this scheme, advantage may be taken of favorable terrain morphology. An example of such terrain is the North Panamint Valley in California where an isolated peak is in the middle of a valley which opens amphitheatrically to the south.
A third scheme for harnessing solar energy proposes to use satellites in geostationary orbit which collect the solar energy, convert it to electrical form and transmit it to earth with microwave beams. Each of the schemes offers the potential advantage of adding a substantial amount of available energy to the declining present resources. Furthermore, these proposals offer to high technology nations the possibility of becoming independent of fossil fuels. However, they all require the investment of substantial amount of new technology which postpones their actual development. In addition, they lack inherent provisions for energy storage to meet fluctuating demands.